Directions : Read the following texts and choose the best alternative to complete each blank space.
Passage 1 Cats and Aids
     The strange illness first surfaced in three cats in California, shortly after AIDS began spreading in the human….1….in the early eighties. A distressed cat lover had brought her….2….pets to Niels Pederson, a professor of veterinary medicine at the University of California at Davis, suspecting that the animals were suffering from an AIDS-like…3…. The cats, which later died, were….4….by many diseases, including respiratory infections and lesions of the mouth and skin.
     Studies have since….5…..that the cats were indeed infected by a virus that has much in common with the human AIDS virus. Feline Immunodeficiency Virus, or FTV, kills T cells and gradually……6…..the failure of the animal’s immune system. Under the microscope, FIV and its human counterpart look frighteningly….7….
     The cat virus’s genes have now been decoded, making a more detailed comparison….8….The cat and human viruses are “cousins”, says John Elder, a molecular biologist at the Research Foundation of Scripps Clinic in La Jolla, who worked with Pederson on the study. But the….9…..from stored blood samples suggests that the cat virus was present long before the ….10….one arrived in this country. “The virus was always there,” says Elder. “but it looked the experience of the AIDS virus to bring it to light.”